Bi-ventricular axial micropump: impact on blood cell integrity.

BACKGROUND AND OBJECTIVE: Off-pump coronary artery bypass grafting has stimulated the development of micro-pumps designed to prevent the hemodynamic instability induced by heart luxation for the exposure of target vessels of the posterior wall. Impella (Aachen, Germany) developed micro-pumps with a miniaturized propeller system for both sides of the heart. The aim of this study was to analyze the impact of both pumps working together on blood cell integrity. MATERIALS AND METHODS: Both right and left-sided micro-pumps were implanted in 5 calves (body weight, 72_4 Kg) during 3 h. Blood samples for hematology and hemolysis parameters were drawn hourly. RESULTS: Both pumps performed well with a flow of 3.6 L +/- 0.3 L during the 3 h of the experiment with stable hemodynamic conditions. Mixed venous oxygen saturation was 63.4 +/- 15.2% at baseline and 63.8 +/- 16.3% at the end of the experiment (P = ns). Red cell count, LDH and free plasma hemoglobin were 6.7 +/- 2.1 x 10(12)/L, 1807 +/- 437 IU/L, and 32 +/- 9 mg/L at baseline vs. 6.1 +/- 2.1 x 10(12)/L, 1871 +/- 410 IU/L, and 52 +/- 9 mg/L at the end of the experiment (P = ns for all comparisons). Platelet count exhibited a non-significant drop (872 +/- 126 vs. 715 +/- 22 x 10(9)/L). CONCLUSIONS: This double pump system based on the Archimed screw principle is hematologically well tolerated under conditions of prolonged cardiac assist.

Design and Characterization of a Biomimetic Piezoelectric Pump Inspired on Group Fish Swimming Effect

Flow pumps are important tools in several engineering areas, such as in the fields of bioengineering and thermal management solutions for electronic devices. Nowadays, many of the new flow pump principles are based on the use of piezoelectric actuators, which present some advantages such as miniaturization potential and lower noise generation. In previous work, authors presented a study of a novel pump configuration based on placing an oscillating bimorph piezoelectric actuator in water to generate flow. It was concluded that this oscillatory behavior (such as fish swimming) yields vortex interaction, generating flow rate due to the action and reaction principle. Thus, following this idea the objective of this work is to explore this oscillatory principle by studying the interaction among generated vortex from two bimorph piezoelectric actuators oscillating inside the same pump channel, which is similar to the interaction of vortex generated by frontal fish and posterior ones when they swim together in a group formation. It is shown that parallel-series configurations of bimorph piezoelectric actuators inside the same pump channel provide higher flow rates and pressure for liquid pumping than simple parallel-series arrangements of corresponding single piezoelectric pumps, respectively. The scope of this work includes structural simulations of bimorph piezoelectric actuators, fluid flow simulations, and prototype construction for result validation.

A biomimetic piezoelectric pump: Computational and experimental characterization

Flow pumps have been developed for classical applications in Engineering, and are important instruments in areas such as Biology and Medicine. Among applications for this kind of device we notice blood pump and chemical reagents dosage in Bioengineering. Furthermore, they have recently emerged as a viable thermal management solution for cooling applications in small-scale electronic devices. This work presents the performance study of a novel principle of a piezoelectric flow pump which is based oil the use of a bimorph piezoelectric actuator inserted in fluid (water). Piezoelectric actuators have some advantages over classical devices, such as lower noise generation and ease of miniaturization. The main objective is the characterization of this piezoelectric pump principle through computational simulations (using finite element software), and experimental tests through a manufactured prototype. Computational data, Such as flow rate and pressure curves, have also been compared with experimental results for validation purposes. (C) 2009 Elsevier B.V. All rights reserved.

New methods for controlling twin configurations and characterizing twin boundaries in 5M Ni-Mn-Ga for the development of applications

Traditional methods for studying the magnetic shape memory (MSM) alloys Ni-Mn-Ga include subjecting the entire sample to a uniform magnetic field or completely actuating the sample mechanically. These methods have produced significant results in characterizing the MSM effect, the properties of Ni-Mn-Ga and have pioneered the development of applications from this material. Twin boundaries and their configuration within a Ni-Mn-Ga sample are a key component in the magnetic shape memory effect. Applications that are developed require an understanding of twin boundary characteristics and, more importantly, the ability to predictably control them. Twins have such a critical role that the twinning stress of a Ni-Mn-Ga crystal is the defining characteristic that indicates its quality and significant research has been conducted to minimize this property. This dissertation reports a decrease in the twinning stress, predictably controlling the twin configuration and characterizing the dynamics of twin boundaries. A reduction of the twinning stress is demonstrated by the discovery of Type II twins within Ni-Mn-Ga which have as little as 10% of the twinning stress of traditional Type I twins. Furthermore, new methods of actuating a Ni-Mn-Ga element using localized unidirectional or bidirectional magnetic fields were developed that can predictably control the twin configuration in a localized area of a Ni-Mn-Ga element. This method of controlling the local twin configuration was used in the characterization of twin boundary dynamics. Using a localized magnetic pulse, the velocity and acceleration of a single twin boundary were measured to be 82.5 m/s and 2.9 × 107 m/s2, and the time needed for the twin boundary to nucleate and begin moving was less than 2.8 μs. Using a bidirectional magnetic field from a diametrically magnetized cylindrical magnet, a highly reproducible and controllable local twin configuration was created in a Ni-Mn-Ga element which is the fundamental pumping mechanism in the MSM micropump that has been co-invented and extensively characterized by the author.

The gas flow rate increase obtained by an oscillating piezoelectric actuator on a micronozzle

Micronozzles with piezoelectric actuator were fabricated and investigated. The micronozzles were fabricated in glass substrates using a powder-blasting technique, and the actuator is a bimorph structure made from a piezoelectric polymer. The actuator was located at the nozzle outlet, and was driven in an oscillating mode by applying an alternating voltage across the actuator electrodes. With a pressure difference between inlet and outlet, the gas flow rate through the device was increased. This effect was quantified, and compared to a similar micronozzle with no actuator. The increase in the flow rate was defined as the gas flow through the micronozzle with actuator oscillating minus the gas flow without actuator, was found to depend on the inlet pressure, the pressure ratio, and the nozzle throat diameter. (C) 2008 Elsevier B.V. All rights reserved.

Computational and experimental characterization of a low-cost piezoelectric valveless diaphragm pump

Flow pumps act as important devices in areas such as Bioengineering, Medicine, and Pharmacy, among other areas of Engineering, mainly for delivering liquids or gases at small-scale and precision flow rate quantities. Principles for pumping fluids based on piezoelectric actuators have been widely studied, since they allow the construction of pump systems for displacement of small fluid volumes with low power consumption. This work studies valveless piezoelectric diaphragm pumps for flow generation, which uses a piezoelectric ceramic (PZT) as actuator to move a membrane (diaphragm) up and down as a piston. The direction of the flow is guaranteed by valveless configuration based on a nozzle-diffuser system that privileges the flow in just one pumping direction. Most research efforts on development of valveless flow pump deal either with computational simulations based on simplified models or with simplified physical approaches based on analytical models. The main objective of this work is the study of a methodology to develop a low-cost valveless piezoelectric diaphragm flow pump using computational simulations, parametric study, prototype manufacturing, and experimental characterization. The parametric study has shown that the eccentricity of PZT layer and metal layer plays a key role in the performance of the pump.